Resident macrophages of the lung and liver: The guardians of our tissues

Abstract

Resident macrophages play a unique role in the maintenance of tissue function. As phagocytes, they are an essential first line defenders against pathogens and much of the initial characterization of these cells was focused on their interaction with viral and bacterial pathogens. However, these cells are increasingly recognized as contributing to more than just host defense. Through cytokine production, receptor engagement and gap junction communication resident macrophages tune tissue inflammatory tone, influence adaptive immune cell phenotype and regulate tissue structure and function. This review highlights resident macrophages in the liver and lung as they hold unique roles in the maintenance of the interface between the circulatory system and the external environment. As such, we detail the developmental origin of these cells, their contribution to host defense and the array of tools these cells use to regulate tissue homeostasis.

Cellular Distribution and Intracellular Localization of Different Sizes of Fluorescent Thiol-Organosilica Particles in Mouse Lungs

“…Physiologically, macrophages in the lungs clear surfactant and serve as the primary immune response against microbes such as viruses and bacteria. Macrophage dysfunction is associated with lung diseases, such as pulmonary fibrosis, COPD, and pulmonary alveolar proteinosis. , Macrophages have been proposed to be associated with pulmonary fibrosis pathology and have been investigated. , Important associations between CD11c­(+) and CD11b­(+) macrophages and pulmonary fibrosis have also been reported. , Tumor-associated macrophages (TAM) have been well investigated in lung cancer and are associated with cancer cell proliferation, invasion, and metastasis. , In patients with nonsmall cell lung cancer, CD68­(+) TAM infiltration in lung tumors correlates with tumor stage and metastasis. , Associations with various diseases have been reported, even in cells treated with the three surface markers used in this study. Further studies, including the classification of macrophages based on particle uptake, may reveal more specific pathological and physiological mechanisms.…”

“…Macrophage dysfunction is associated with lung diseases, such as pulmonary fibrosis, COPD, and pulmonary alveolar proteinosis. 33,34 Macrophages have been proposed to be associated with pulmonary fibrosis pathology and have been investigated. 35,36 Important associations between CD11c(+) and CD11b(+) macrophages and pulmonary fibrosis have also been reported.…”

PRRSV-2 viral load in critical non-lymphoid tissues is associated with late gestation fetal compromise

“…The first of which is transcriptional upregulation in the tissue resident macrophages, which occurs during the establishment of an activated phenotype ( Etzerodt and Moestrup, 2013 ). Second is that tissue resident macrophages are able to re-enter the cell cycle despite being terminally differentiated ( Kulle et al, 2022 ), so the apparent upregulation could indicate proliferation resulting in a proportional increase of CD163+ cells relative to other constituents. Finally, increased transcription of CD163 could be associated with recruitment of blood monocytes or macrophages from other tissues.…”

Macrophages and stem/progenitor cells interplay in adipose tissue and skeletal muscle: a review

“…For example, bone macrophages are called osteal macrophages (38); alveolar macrophages are in the lungs, microglial cells in the brain, Langerhans cells (LC) in the skin, Kupffer cells in the liver, histiocytes in connective tissue, etc. (39). A separate category is tumor-associated macrophages (TAMs), which populate many types of tumors and, depending on the cancer type and tumor environment, fight or promote cancer development and metastasis (40)(41)(42)(43) Another distinct category, described as a mononuclear phagocytic system (MPS), includes all types of macrophages and their bone marrow (BM) progenitors (44).…”